The invention concerns steering angle sensors comprising a main rotor which can be coupled to a steering column or steering wheel to be rotated synchronously therewith, and at least one additional rotor which can be driven by the main rotor, a first scanning unit for scanning the rotational angle position of the main rotor, and a second scanning unit for scanning the rotational angle of the additional rotor.
There are conventional steering angle sensors which are based on an optical principle. A steering angle sensor of this type may comprise a rotor with code discs whose code can be scanned by a scanning unit. The code of the code discs is usually realized by teeth of different width with intermediate gaps. The teeth or the gaps can be detected by optical means, in particular, by photocells. The code for determining the rotational angle position of the steering wheel can only achieve a resolution on the order of magnitude of approximately 1.5° due to manufacturing limits.
The use of optical means is also disadvantageous since, after long operating times, in particular when used in a vehicle, the optical means are subject to wear due to soiling. The production of code discs is moreover relatively demanding.
In order to improve the resolution, DE 101 10 785 A1 proposes use of a counting wheel which is driven by a rotor having a code disk. The rotational angular position of the counting wheel may be set by two magnetic field sensors disposed at an angular offset with respect to each other of 90° and be used for calculating the absolute steering wheel angle. This embodiment improves the above-mentioned resolution by a factor of approximately 2.
DE 195 06 938 A1 discloses a steering angle sensor for driving two additional rotors using a main rotor, wherein the rotational angular position of the additional rotors can be detected by sensors. The angular position of the main rotor can be mathematically detected via the rotational angular position of the additional rotors driven by the rotor. A resolution of up to 0.1° can thereby be achieved.
DE 195 06 938 A1 is disadvantageous in that at least two rotational bodies are required, in addition to the rotor. These require a relatively large amount of space. Moreover, the rotational bodies must be driven by the driver of a vehicle provided with such a steering angle sensor, which either increases the required actuation forces or requires increased steering support.
Departing therefrom, it is the underlying purpose of the present invention to provide a compact steering angle sensor with maximum resolution.